Gamma Knife Radiosurgery for Pituitary Adenomas Invading the Cavernous Sinus: Tokyo Women's Medical University...

Total surgical removal of a pituitary adenoma (PA) invading the cavernous sinus (CS) is challenging and carries a significant risk of postoperative complications. As an alternative treatment strategy, after incomplete resection, such tumors may undergo stereotactic radiosurgery-in particular, Gamma Knife surgery (GKS). Treatment planning based on advanced neuroimaging (e.g., thin-slice 3-dimensional postcontrast constructive interference in steady state (CISS) images) allows clear visualization of the target microanatomy, which results in highly conformal and selective radiation delivery to the lesion with preservation of adjacent functionally important neurovascular structures. In the Tokyo Women's Medical University experience of GKS for 43 nonfunctioning and 46 hormone-secreting PA invading the CS, with a minimum follow-up period of 5 years (mean 76 months, range 60-118 months), the tumor control rate has reached 97%, and a significant volume reduction (≥50%) has been seen in 24% of lesions. In cases of hormone-secreting neoplasms, normalization (in 18 patients; 39%) or improvement (in 22 patients; 48%) of endocrinological function has been noted. Importantly, such effects have been sufficiently durable. Complications have been extremely rare and limited to transient cranial nerve palsy (in 2% of cases). Notably, no patient in our series has had a new pituitary hormone deficit after irradiation. Thus, subtotal resection followed by GKS may be considered a valuable alternative to aggressive surgery for a PA invading the CS.